重离子储存环CSRe上类钠Kr^(25+)离子的双电子复合精密谱学实验研究

Dielectronic recombination experiment of Na-like Kr^(25+)at heavy ion storage ring CSRe

高电荷态离子的双电子复合精密谱学实验研究,不仅对天体等离子体和聚变等离子体的研究具有重要意义,而且可以作为一种新的精密谱学工具,用来检验强场量子电动力学效应、测量同位素移动及提取原子核电荷半径等.在兰州重离子储存环CSRe上,安装了专门用于电子-离子复合精密谱学实验的电子束能量调制系统,质心系下电子-离子碰撞能量的调制范围达到0—1 keV.在CSRe电子冷却器下游安装了自主研制的塑料闪烁体探测器和多丝正比探测器,用于探测复合离子.在此基础上,使用Kr^(25+)离子在CSRe上进行了首次双电子复合测试实验,实验测量了质心系能量0—70 eV的双电子复合速率系数.为了更好地理解实验测量结果,利用FAC(flexible atomic code)程序计算了Kr^(25+)离子的双电子复合速率系数,并与实验做了细致对比,整体符合很好,而且发现3s→41(△n=1)的共振跃迁对实验谱线有很大的贡献.实验结果表明,CSRe双电子复合实验平台具有非常好的稳定性和可重复性,能够为下一步开展更高电荷态离子的双电子复合精密谱学实验、检验强场量子电动力学效应以及原子核性质精密测量等前沿实验提供支持.

The experimental study of precision spectroscopy of dielectronic recombination(DR)of highly charged ions is not only important for astronomical plasma and fusion plasma,but also can be used as a new precision spectroscopy to test the strong-field quantum electrodynamic effect,measure isotope shift,and extract the radius of atomic nuclei.An specially designed electron beam energy detuning system for electron-ion recombination precision spectroscopy experiments has been installed on the heavy ion storage ring CSRe in Lanzhou,China,where the electron-ion collision energy in the center-of-mass system can be detuned to 1 keV,and an independently-developed plastic scintillator detector and multiwire proportional chamber detector have been installed downstream of the electron cooler of the CSRe for detecting recombined ions.The multiwire proportional chamber detector has the ability to non-destructively monitor the profile of the ion beam in realtime while acquiring the recombined ion counts,providing guidance for optimizing the ion beam.On this basis,the first test experiment on dielectronic recombination of Kr^(25+)ions is carried out at the CSRe,and the dielectronic recombination rate coefficients in a range of 0-70 eV in the frame of center-of-mass are measured.In order to fully understand the experimental results,we calculate the dielectronic recombination rate coefficient of the Kr^(25+)ion by using the flexible atomic code(FAC)and make a detailed comparison with the experimental result,showing that they are in good agreement with each other,and only the resonance energy values of the two resonance peaks at 1.695 eV and 2.573 eV are significantly different.In addition,the DR resonance energy values and intensities are obtained by fitting the experimental results in a range of 0-35 eV,and we find that the transition 3s→4l(Δn=1)contributes significantly to the experimental spectral lines.Furthermore,we compare the plasma rate coefficients derived from the DR rate coefficients with those derived from the AUTOSTRUCTURE and FAC theories,which differ by 20 percent in a temperature range less than 106 K.The experimental results show that the DR experimental platform of the CSRe has very good stability and reproducibility,and can provide support for the future DR experiments of highly charged ion,i.e.for testing strong-field quantum electrodynamics effect and measuring the properties of atomic nuclei.